Acoustic Feedback

Complete audio systems involve some acoustics, by which we mean the way sound waves radiate, both in the air and through floors, ceilings, etc. The subject of concern in audio is called electro-acoustics, because it deals with the combination of electronic and acoustic effects.

Acoustic feedback

An amplifier can become unstable because high-level audio (electrical power) at the output is fed back to the low-level input circuits. It can also become unstable because high-level acoustic energy radiated from the loudspeaker is fed back to a microphone. This occurs in public address systems where the complete system consists of a microphone, an amplifier, and loudspeakers to reinforce the sound of the speaker on the platform, or the orchestra on stage. Acoustic feedback is not limited to systems possessing microphones; it can also occur in a home reproducing system due to a tube, or the phonograph pickup, acting as a microphone,... It. does this by picking up either sound waves from the air or acoustic vibrations coming through the floor or walls. For this reason, care has to be taken to insure that high-level vibration cannot reach the turntable, the pickup, or any of the amplifying tubes that handle low-level audio if they are at all microphonic.